Poly-o-aminobenzoate (POA) was prepared by oxidizing o-aminobenzoic acid with (NH4)(2)S2O8 in an acidic solution. POA was adsorbed on TiO2 nanocrystal surface to obtain a POA-TiO2 nanocomposite. The polymerization reaction, structure, adsorption reaction on TiO2 surface, and visible light sensitization effect of the polymer adsorbed on TiO2 surface were studied by FT-IR and UV-visible spectra, cyclic voltammetry, and measurements of visible light photoelectrochemical and photocatalytic activities. Three kinds of POA with different long conjugate structures can be formed. These polymers have large absorbance in wide visible light region. POA molecules can be adsorbed on TiO2 surface by anchoring their carboxylate groups to the TiO2 surface with a multi-bridging chelating mode, which causes formation of the POA-TiO2 nanocomposite with a high stability. POA adsorbed on the TiO2 nanocrystal showed high visible light sensitization effect in the photocatalytic reaction. (C) 2010 Elsevier B.V. All rights reserved.